Integrally bladed rotors have either a disk-shaped or a ring-shaped main body having blades integrally provided on the outer periphery thereof. A rotor having a disk-shaped main body is called “blink” (bladed disk), and a rotor having a ring-shaped main body is called “bling” (bladed ring).
Methods for manufacturing integrally bladed rotors are described in Patent Application WO 2005/024185 of the Applicant. In one method, the rotors and their blades are milled from a solid piece of material. In another manufacturing method, the blades are manufactured separately from the main body of the rotor and subsequently attached to the rotor main body using a joining method. Examples of joining methods include linear friction welding, inductive pressure welding or diffusion welding. In the case of the latter manufacturing method, the blading is constituted by forged parts which are already adapted to the desired blade shape in such a manner that after attachment to the rotor main body, only fine machining needs to be performed. However, the blading may also be constituted by a plurality of blade blanks, which are severed from a pressed shape and machined to their desired shape only after they are attached to the rotor main body.
International Patent Application WO 2008/046388 of the Applicant describes a method for manufacturing an integrally bladed rotor, in which at least portions of the rotor are manufactured using a generative method. WO 2008/046388 proposes, in particular, that the blading, or the entire rotor including the blading, be manufactured generatively.
However, since the blades are integrally provided on the rotor main body, replacement of an old blade, such as a damaged blade or one that has reached its maximum life, requires a relatively large amount of effort compared to conventionally manufactured rotors, where the blades are inserted into the main rotor body.
A known method for replacing a damaged blade of an integrally bladed rotor is disclosed in German Patent Application DE 10 2005 033 625 A1 of the Applicant. In this method, the damaged blade is cut off and replaced by a new one that is manufactured using a powder-metallurgical injection molding method. However, German Patent Application DE 10 2005 033 625 A1 does not provide information on whether the new blade is mounted directly on the outer periphery of the rotor main body or whether it is joined to a blade stub left on the rotor main body by the damaged blade that has been cut off.
German Patent Application DE 39 09 733 A1 proposes a method for replacing a blade, in which the new blade is welded to a stub on the rotor main body. The damaged blade is cut off at a defined distance from the rotor main body, leaving a stub whose radial surface provides a blade connection surface for the new blade. In order to stabilize the stub during the joining of the new blade, the stub is stabilized at its circumference by a multi-part metallic collar which forms a metallurgical bond with the stub and the new blade. The height of the collar corresponds to the radial length of the stub, so that the stub and the collar provide the blade connection surface for the new blade. After the joining process, surplus material of, for example, the collar is removed and the stub-new blade connection is machined to its desired final size.
European Patent EP 1 535 692 B1 also describes a method for replacing a blade, in which a blade stub left on the rotor main body by a damaged blade that has been cut off is stabilized during the joining of the new blade. A framing is created around the stub, into which a metal powder is filled. The new blade is attached by friction welding to a radial blade connection surface of the stub, during which process the metal powder forms a stabilizing coating for the stub. After the joining of the new blade, the stub-new blade connection is machined to its desired final size.
However, from European Patent EP 0 376 874 B1 it is also known that instead of stabilizing the stub on the rotor main body, the new blade can be provided with a collar in the region of its joining surface to allow for uniform heating and prevent deformation during the joining process. The separation of the damaged blade can be accomplished using the electrical discharge machining (EDM) method. After the joining of the new blade, the collar and surplus material are removed and the stub-new blade connection is machined to its desired final size.
U.S. Pat. No. 6,095,402 presents a method for manufacturing or repairing an integrally bladed rotor, in which a new blade is also mounted on a blade stub left on the rotor main body by a damaged blade that has been cut off. The subject-matter of this U.S. patent is directed to the particular geometric configuration of the blade connection surface of the stub, so that the new blade can be joined by linear friction welding even if the blade connection surface is not plane.
The aforementioned known methods have in common that the radial blade connection surface of the stub is formed during the separation of the damaged blade. A separation surface formed during the separation of the damaged blade serves as a blade connection surface for a new blade. In order to prepare the joining process, the separation surface is merely suitably cleaned. This has the disadvantage that the damaged blade must be cut off at a defined distance from the outer periphery of the rotor main body and, in addition, that the cutting must be performed very accurately to allow for precise joining of the new blade. This requires the use of technically complex cutting methods. Another disadvantage is that either the stub must be stabilized in a complex manner during the joining process, or the new blade must have special design features because the finished shape of the stub is unable to withstand the loads occurring during the joining process.